The instant invention is directed to an improved, automatic (i.e. pressure regulating, at least in part) industrial-scale fire fighting foam nozzle, the foam nozzle operable with and without a self-eduction feature. Improved features include automatically self-metering concentrate into the flow of the primary fire-fighting fluid (typically water) as the flow rate varies, a feature made particularly pertinent by the automatic aspect of the nozzle. The flow rate in “automatic” (i.e. pressure regulating) nozzles varies significantly more than in “fixed flow” nozzles.
Improved features also include selective valving in order to automatically accommodate and self-meter for different additive concentration levels or “ratios” or percentages, as well as a mechanically operable flowmetering capability.
Terms
“Industrial-scale” as used herein refers to nozzles designed to fight industrial fires and indicates flow rates at least equal to 50 gpm, and which typically run to greater than 1000 gpm.
“Automatic” refers to a nozzle's capability, at least for a portion of its flow rate range, to automatically adjust the nozzle's discharge orifice in order to maintain (at least approximately) a targeted discharge pressure (and thus to tend to maintain a nozzle's range) when or while flow rates or pressures supplied to the nozzle vary.
“Self-metering” refers to an automatic nozzle's capacity to automatically adjust the amount of foam concentrate or additive pumped (whether or not by self-eduction, in whole or in part) into a nozzle's main stream of fire fighting fluid as flow rate of the primary fire fighting fluid through the nozzle varies. Self-metering, thus, targets maintaining a given ratio of concentrate or additive to fire fighting fluid as or while fire fighting fluid flow rate varies.
“Selectable” refers to a capacity to select one of a plurality of concentrate or additive ratios in order for the self-metering feature to then meter for this selected ratio.
“Self-eduction” refers to a jet pump type design, or eductor, built into or onto a nozzle such that a flow of the primary fire fighting fluid to and/or through the nozzle at least assists to draw or pump a foam concentrate or additive into the nozzle.
Background
Maintaining an approximately constant discharge pressure for a nozzle tends to yield a constant range and “authority” for the discharge from the nozzle. As a consequence, however, nozzle flow rate tends to vary significantly, reflecting rather directly variations in supply of fluid to the nozzle.
In certain applications, such as in vapor suppression, it is particularly useful for a fixed-location fire fighting nozzle to self regulate in order to discharge at an approximately constant, or targeted, pressure, because the discharge pressure governs what is referred to as the “authority” of the discharge stream and to a significant extent the stream's range. A “constant discharge pressure” nozzle comes closer to delivering a consistent stream at a fixed range than does a “fixed flow” designed nozzle. A fixed range is more desirable for a fixed-location nozzle with a fixed target.
One particular application in which a self-metering pressure regulating nozzle is useful is in a system of permanently stationed nozzles around locales subject to the leakage of toxic chemicals. Upon leakage, a permanently stationed configuration of relatively constant pressure nozzles (understanding that pressure regulation in a nozzle is only approximately achievable), possibly under remote control, can be activated to provide a predesigned curtain of water/fog to contain and suppress any toxic vapors. In such circumstances it may be optimal for nozzles to discharge their fluid with a constant range and authority as opposed to having their discharge structured and regulated for a relatively constant flow rate, as is more typical for “fixed flow” design fire fighting nozzles. Water/fog created with approximately constant range and authority, while operating under conditions of varying supply pressure, can more reliably curtain a preselected region from a fixed locale.
Typically, mobile fire fighting nozzles are designed as “fixed flow”, structured to deliver an (approximately) pre-set level of gallons-per-minute flow, assuming a nominal supply of head pressure, such as 100 psi at the nozzle. When the head pressure actually available to a “fixed flow” nozzle in an emergency varies, flow rate tends to remain more constant in such designs than range. (Again, structuring a nozzle to target and regulate “discharge pressure” tends to let flow rate vary with variations in delivered pressure while keeping range more constant.)
A “hybrid” nozzle is a combination of “pressure-regulating” and “fixed flow” nozzle design features. It is designed to discharge fire extinguishing fluid at a pre-selected discharge pressure (and thus range) up to a targeted flow rate; thereafter it is designed to maintain a relatively constant flow rate while discharge pressure (and the range) are allowed to increase with supply pressure. A preselected discharge pressure, for example, would likely be 100 psi, but the preselected pressure could vary, and might more optimally be selected to be 120 psi. A targeted flow rate would be preselected and approximate. This “hybrid” design combines the benefits of maintaining range at low supply pressures (on low supply flow rates) while maintaining flow rate at nominal or higher supply pressures (on flow rates), thereby accommodating minimum range requirements, on the one hand, while, on the other hand, more easily accommodating self-educting features and/or a capacity to throw chemicals such as dry powder for nominal or higher supply pressures and flow rates.
The invention herein is compatible with both automatic or semi-automatic (hybrid) nozzles. It is compatible with self-educting foam nozzles, including enhanced eductive techniques, for both peripheral and central channeling, which enhanced eduction can be particularly helpful in automatic nozzles or when throwing chemicals such as dry powder, as well as non-self-educting foam nozzles.
Nozzle Basics
A fire fighting nozzle may be designed to be preadjustable to operate at a preselected fixed flow over a range of fixed flows compatible with the nozzle in design, such as from 500 gallons-per-minute to 2000 gallons-per-minute, given a certain nominal discharge pressure and flow supply (typically assumed to be around 100 psi). The preadjustment may be effected, for instance, by hand screwing a baffle in or out. By contrast, in an automatic nozzle that self regulates for pressure while allowing flow to vary, nozzle design typically incorporates an automatically self-adjusting baffle or the like, proximate the nozzle discharge. When fluid pressure at the baffle, sensed directly or indirectly, is deemed to lie below the targeted pressure, the baffle is structured in combination with the nozzle body to “squeeze down” on the effective size of the discharge orifice or gap. (The targeted pressure, in turn, can be adjusted by adjusting a pilot valve or other sensing mechanism, for example.) When pressure builds up at the baffle, sensed directly or indirectly, to exceed the preselected target pressure, the baffle is structured to shift to enlarge the effective size of the nozzle discharge orifice or gap. Enlargement continues, in general, until the discharge pressure reduces to the preselected target value. Adjustments in the size of the discharge orifice or gap, in accordance with this technique, allows flow rate through the nozzle to vary significantly while the discharge tends to have a constant discharge pressure, and thus a constant “authority” and range.
A hybrid design includes a further adaptation in self-adjusting nozzles. To continue to review the basics of a nozzle, a fire fighting nozzle defines a conduit for a fire fighting fluid that terminates in a discharge orifice. (The fire fighting fluid is usually water, and while it may be treated and discussed as water herein, it should be understood that nozzle technology is applicable to various fire fighting fluids.) The conduit and discharge orifice structure are typically designed in combination to recover, to the extent practical, fire fighting fluid pressure available from the fluid source. Recovery of pressure affects range.
Given generally anticipatable supply ranges for the fire fighting fluid, in pressure and in flow (industry standard sources of pressurized water might be anticipated to vary between 75 psi and 150 psi), nozzle body conduits and discharge orifices are designed to cover effective, or practical, flow windows. For instance, a “two and one-half inch” nozzle might be adjustable to effectively flow between 150 GPM and 600 GPM while a “sixteen inch” nozzle might be adjustable to effectively flow between 4,000 GPM and 16,000 GPM, both being affected by variations in supply pressure and quantity of fire fighting fluid.
Adjustable discharge orifices, either of the automatic (pressure-regulating) or manual (fixed flow) varieties, are designed to be adjusted within the range of flow effectiveness available for the nozzle body dimensions. Fluid flow rate through a given nozzle may be allowed to vary within the nozzle's effective flow window, also taking into account variations in fluid supply and pressure. Minimum limits on an effective flow window for a nozzle include a minimum effective “gap” size, or a minimum effective width of a typically annular discharge orifice for the nozzle. Below a certain “gap” size the thickness of the wall of water discharged diminishes to an extent that the water wall tends to disintegrate and nozzle throw performance suffers. On the other end, a “gap” can get so large that the fixed conduit bore structure of the nozzle itself governs throw. Thus, there are practical limits to the flow of water that can be efficiently and effectively flowed through a given nozzle bore size.
(It should be understood that although adjustable discharge orifices for fire fighting foam nozzles are traditionally designed in terms of an adjustable baffle within a fixed conduit, any element of nozzle structure defining at least in part the discharge orifice, including an outer wall portion, in theory, could be an adjustable element. One refers to traditional designs for convenience, in regard to an adjustable baffle located in a conduit where the adjustment of the baffle forward and backward governs gap size.)
Again, for a given nozzle size, there is a range in which baffle adjustment is effective and efficient. The range correlates with an effective or practical fluid flow window for the nozzle.
A given conduit and discharge orifice contribute to define a “k” factor for a nozzle. Flow rate and discharge pressure are related by the formula: r=k√p, where r is the flow rate, p the discharge pressure and k the “k” factor. It can be seen that for a constant k, flow varies with the square root of pressure. With a fixed conduit and discharge orifice, discharge pressure p rises with increased supply pressure from the fluid source while flow rate “tends” to remain relatively constant, at least as compared to pressure, because it only increases with the square root of pressure.
Automatic Nozzles
“Automatic” nozzles have automatically adjustable discharge orifices. Automatically adjustable discharge orifices, as discussed above, are typically designed to maintain a preselected targeted discharge pressure, such as 100 psi. In automatic nozzles there is typically a means for sensing discharge fluid pressure and a biasing means structured to adjust the discharge orifice (sometimes referred to as the “gap”) until the sensed discharge pressure is approximately a preselected targeted discharge pressure. (The word “approximately” is used herein and throughout because automatic nozzle designs are only “approximately” accurate.) As a result of sensing and adjustment, a discharge orifice or gap is narrowed or widened in an automatic nozzle so that the sensed discharge pressure is approximately the selected discharge pressure. Again, as discussed above, when the discharge orifice or gap is narrowed, fluid flow rate through the nozzle is reduced. As the gap is widened, fluid flow rate through the nozzle is increased. If the discharge orifice of the nozzle were to remain fixed, the “k” of the nozzle would remain fixed and flow rate would “tend” to remain fixed while discharge pressure would vary with supply pressure. (Flow rate varies only with the square root of pressure.).
Foam Nozzles
Advantage of constant flow rate. As foam concentrate or additive is designed to be metered into a fluid stream at a constant percent (e.g. 3% or 6% or the like), a relatively constant flow rate of the fluid stream is an advantage as it allows relatively simple metering devices for the foam concentrate to be set. A constant flow rate with a high discharge pressure is also an advantage, as high pressure helps some concentrates create better foam. In a nozzle that discharges a chemical, such as a dry powder within a fire fighting fluid, constant flow rate may be an advantage in order to limit fluid flow rate so as to avoid unnecessary wetting of the powder. Furthermore, nozzles that adjust essentially without limitation to target a selected discharge pressure, thereby allowing flow rate to rise without limit, can waste water when there is a limited supply of water.
Advantage of constant pressure. Although a relatively constant flow rate from a nozzle can be an advantage in many situations, if the supply pressure is weak or if a nozzle is set at a fixed distance from a fire, a relatively constant pressure can be an advantage. Constant pressure tends to maintain range for a nozzle, even though flow rate may diminish.
Within the time span of one fire, the relative importance of constant pressure and of constant flow rate can shift.
A “hybrid”, or “selectively automatic” nozzle, combines the two worlds, constant flowrate and constant pressure. An adjustable stop (or any other such adjustable means) can be set so that an automatically adjustable discharge orifice is provided, as in an automatic nozzle, for flow rates up to a given point, a preselected target (in a nozzle's effective flow window). When supply pressure goes low, range is maintained. However, if and/or when targeted fluid flow rate within the nozzle is reached, the stop or the like causes the discharge orifice to cease adjusting. Discharge pressure rises with supply pressure but fluid flow rate tends to remain constant (again, rising only in proportion to the square root of the pressure). Metering in a foam concentrate in a preselected proportion or ratio is more reliable.